Predetermined-torque-applying wrench with thrust operated torsion bar



QN. NN

NELSON PREDETERMINED-TORQUE-APPLYING WRENCH WITH ,THRUST OPERATED TORSION BAR Filed Sept. 20, 1957 July 2l, 1959 United Sttes PREDETERhDNED-TORQUE-APPLYING WRENCH WITH THRUST OPERATED TRSION BAR Gorman R. Nelson, Sioux Falls, S. Dak.

Application September 20, 1957, Serial No. 685,134

14 Claims. (Cl. 31-5Z.3)

This invention relates to wrenches of the type for limiting the maximum torque to be applied to a workpiece, such as a nut or bolt.

An object of my invention is the provision of a new and improved reciprocating type torque wrench of simple and inexpensive construction and operation.

Another object of my invention is to provide a novel reciprocating type torque wrench applying, when reciprocated, a predetermined torque to the workpiece.

Still another object of my invention is the provision of a novel and improved reciprocating type torque wrench for applying to a workpiece, a torque, the magnitude of which is related to the length of reciprocating movement of the wrench.

A further object of my invention is the provision in a reciprocating type torque wrench of an improved control apparatus for limiting and varying the maximum torque applied to the workpiece.

These and other objects and advantages of my inven` tion will more fully appear from the following description made in connection with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views and in which:

Fig. l is a longitudinal section View through the tool with portions of certain` parts being shown in elevation adjacent the longitudinal axis or center line;

Fig. 2 is an elevation View, partly in section, showing the tool lin a position different from the position shown in Fig. l;

Fig. 3 is a transverse sectional view taken substantially on a plane as indicated at 3-3 in Fig. l; and

Fig. 4 is a longitudinal sectional View of a modiiied form of the invention which is power operated.

The form of the invention shown in Figs. 1-3 includes a reciprocable thrust member, indicated in general by the numeral 1t) which is movable longitudinally along an elongated resilient torsion bar or rod 11, the opposite ends 11a and 11b of which are rotatable with respect to each other within the elastic limits of the bar 11. The invention also includes means for rotating the rear end 11b of bar 11 in response to reciprocating movement of the thrust member in an axial direction and also includes coupling apparatus 12 affixed to the front end 11a of the torsion bar 11 and adapted for attachment with a workpiece, such as a nut or bolthead, to be turned. The tool construction also includes means rigid with the opposite ends of the torsion bar 11 in Stich a manner as to prevent transverse flexing of the bar 11 due to such causes as transversely directed forces thereon or longitudinal thrust thereon, but said rigid means provides a rotatable connection to permit one end of the bar 11 to rotate relative to the other `end thereof.

The thrust member 1t) includes an elongated rigid thrust element or tube 13 having thereon a mounting ring 14 with a pair of diametrically opposed, countersunk apertures 15 therethrough and adapted to receive screws 16. The thrust member 1t! also includes a tubular handle 17 which is threadably or otherwise secured at 2,895,359 Patented July 21, 1959 18 to the mounting ring 14. The outer end of handle 17 has an end closure portion 19 with an inwardly extending spring mounting boss 20 formed integrally thereof and defining an inwardly facing stop or abutment surface 21.

The thrust member 10 also includes a stop element or sleeve 22 telescopically related and adjustable with respect to the inner end of the tube 13 and movable therewith. Sleeve 22 has a scale 23 thereon which may be calibrated in inch-pounds for purposes hereinafter more fully set forth. The rear end of the sleeve 22 defines an annular stop or abutment surface 24.

Releasable means are provided for securing the sleeve 22 in the desired telescopically adjusted position with respect to the tube 13. In the form shown, such means include a sleeve-clamping ring 25 encompassing the sleeve 22 and having at the rear portion thereof a cylindrical surface Z6, received into the open forward end of the tube 13. The ring 25 also has an annular abutment shoulder surface Z7 engageable with the end of the tube 13, and a forward sleeve-clamping portion with an outer, generally conical surface 28 tapering inwardly and forwardly. The forward portion of the ring 25 also has a plurality of longitudinally extending slits 29 therein which deiine therebetween a plurality of radially inwardly` movable sleeve-clamping jaws or ears 30. It will be noted that the forward edge portion 31 of the sleeve-clamping ring Z5 defines an indicator foi use with the scale 23 on the sleeve 22.

A locking nut 32 is threadably connected at 33 to the forward end of the tube 13 and the nut 32 has a radially inwardly facing conical surface 34 of complementary configuration in relation to the surface 28 of ring 25 for engaiging the jaws 30 and urging the same inwardly as the nut 32 is screwed onto the tube 13. By operation of the lock nut 32, the sleeve 22 may be xed in a desired telescopically related position with respect to the tube 13 or may be loosened to permit longitudinal adjustment thereof.

The means for producing rotation of the rear end 11b of the torsion bar 11 includes a hollow rotary shaft 35 within the tube 13. The shaft 35 is longitudinally movable and rotatable with respect to the tube 13. `Shaft 35 defines a helical cam in the outer surface thereof and more specically has a pair of diametrically opposed helical grooves or channels 36 and 37 formed in the outer periphery thereof. lt will be noted that the grooves or channels 36 and 37 open through the rear en d of the shaft 35 as at 37a. The grooves or channels 36 and 37 dene helical camming surfaces 36h and 37b at the opposite sides thereof.

Cam followers 38 and 39, which in the form shown comprise rollers or ball bearing assemblies, are disposed in cooperative camming relation with respect to the helices in the shaft 35. The rollers 33 and 39 are mounted on studs 40 and 41 respectively which extend through apertures 42 in the tube 13 and bear against the mounting ring 14 in alignment with the apertures 15 therein. The screws 16 are threadably secured in tapped apertures in the studs 40 and 41 and thereby securely hold the studs and the cam following rollers 38 and 39 to the mounting ring 14.

Means are provided for connecting the rear end 11b of the torsion rod 11 with the rotary shaft 35. 'Ihe torsion rod 11 extends through the longitudinal and concentric opening 43 through the shaft 35. An end plug or sleeve 44 is affixed onto the end 11b of torsion rod 11 as by a set screw 45. The rod-mounting sleeve 44 is aixed in an enlarged end portion 43a of the central opening 43 in shaft 35 by means of a set screw 46.

The apparatus 12 for coupling the forward end 11a of the torsion bar 11 to a workpiece, such as a nut or bolt head, includes an end plug or mounting 47 which has a hole 48 therein into which the end 11a of the torsion rod 11 extends. The end of the torsion rod 11 is atlixed in the plug- 47 by any suitable means, and in the form shown, the rod is secured to the plug by welding 49. The plug 47r has a threaded stud 50 which may be formed integrally therewith and which projects forwardly in substantial alignment with the rotation axis of the rod 11. A substantially cylindrical coupling element 51 has a threaded, longitudinally extending opening 52 therein which threadably receives the stud t) for interconnecting the coupling element 51 with the front end of the torsion rod 11. The coupling element 51 has a hexagonal socket 53 in the forward end thereof for receiving a bolt head or nut of proper size or for receiving an' adapter A shown in dotted lines in Fig. 1.

The abutment means for limiting the magnitude of rearward longitudinal sliding movement of the thrust member in relation to the shaft 35 includes the forward end surface 54 of the shaft 35 which is in alignment with the stop or abutment surface 24 of the sleeve 22 for abutting thereagainst when the thrust member 10 is fully retracted, as seen in Fig. 1. The abutment means for limiting forward movement of the thrust member 10 includes the abutment surface 21 at the end of the handle 17, and also includes a flat head screw 55 in alignment with the surface 21 and carried by an annular mounting element 56 having a threaded opening 57 longitudinally therethrough, and a nut 5S on the screw 55 which locks the screw in the desired position on the mounting 56. Mounting 56 bears against a rear end of shaft 35 but is freely rotatable thereon, and is held against the end of shaft 35 by means of a compression spring 59, the forward end of which bears against an annular shoulder surface 60 of the mounting 56, and the rear end of which encircles the boss 20 and bears against the closure portion 19 of the handle 17. When the thrust member 1t] is projected forwardly in relation to the shaft 35, the screw head 55 Will bear against the surface 21 and restrict forward shifting of the thrust member and thereby limit the arc through which the rear end of the torsion rod 11 may be turned.

In this form of the invention, the means by which transverse flexing of the torsion rod 11 is prevented, includes a rigid tube 61 in concentric and encompassing relationwith the rod 11 and in end-to-end relation with the shaft 35. The rear end 62 of the tubular member 61 is axed to the shaft 35 for rotation therewith. In the form shown, the rear end 62 of the tube 61 is affixed in an enlargement 43b of the longitudinal opening 43 in the shaft 35 in a sweat fit. Tube 61 is thereby rigid with the shaft 35 to define an integral rotary member.

The forward end 63 of the tube 61 is threadably connected at 64 to a sleeve 65 which has a radially inwardly projecting annular seating portion 66 upon which a bearing 67 is seated so as to be immovable rearwardly with respect to the sleeve 65 and tube 61. The bearing 67 rotatably mounts the coupling element 51 to hold the same in alignment with the rear end 11b of the torsion rod11. It will be noted that a shoulder surface 68 of the coupling element 51 engages the bearing 67 so as to cause the tube 61 and sleeve 65 to carry the entire thrust load which may be exerted against the coupling element 51, so as to prevent any of this thrust load being exerted onto the torsion rod 11 which might cause flexing thereof.

In the operation of this form of the invention, the coupling element 51, or the adapter A, will be applied to the workpiece such as a bolt head or nut. The handle 17` will be manually gripped and the entire thrust member 10 will'be longitudinally moved along the rotation axis of shaft 35, causing the cam followers 33 and 39 to engage the camming surfaces 3611 and 37b of the grooves 36 and 37 whereby to cause rotation of the shaft 35 and corresponding rotation of the rigid tube 61 and the sleeve 65. Rotation of the shaft 35 causes rotation, through an identical arc, of the rear end 11b of the torsion rod 11. Rotation of the rearend of the torsion rod 11 tends to cause rotation of the front end 11a thereof. In order to accurately torque the workpiece or bolt, it must previously have been drawn up so that the head is seated on the part being held. 1f the workpiece or bolt head does not turn, of course the coupling element 51 will not turn, nor will the forward end 11a of the torsion rod 11. In this event, the magnitude or torque applied to the workpiece is in direction relation to the arc of rotation of the rear end 11b of the torsion rod 11. t will therefore be seen that the torque applied to the workpiece is thereby in direct relation to the magnitude of longitudinal shifting movement of the thrust member 10.

When the surface 21 of the handle 1'7 engages the screw head 55, the shaft 35 will be stopped and no more torque will be applied to the workpiece.

When the tool is removed from the workpiece, the spring 59 will urge the shaft 35 forwardly in relation to the thrust member 10, or stated the other way, the spring 59 will urge the thrust member 10 rearwardly along the shaft 35, until the rear end surface 24 of sleeve 22 en gages the abutment surface 54 at the front end of the shaft 35. Further rearward movement of the thrust member 1t) in relation to the shaft 35 is thereby precluded. 1t will thereby be seen that the starting position of the thrust member 10 in relation to the shaft 35 is defined by the adjustment of the sleeve 22. If the lock nut 32 is loosened so as to loosen the jaw elements 3@ from the sleeve 22, the sleeve 22 may be telescopically adjusted in relation to the tube 13. 1f less torque is to be applied to the workpiece, the sleeve 22 will be retracted into the tube 13, and if additional torque is to be applied to the workpiece, the sleeve 22 will be projected outwardly from the tube 13. lf the sleeve 22 is adjusted so that the indicator 31 is opposite the scale mark 6 (inch pounds) and the lock nut is then tightened so as to x the sleeve 22 in this new position, it will be seen that the thrust member 1@ will not be allowed to move rearwardly in relation to the shaft 35 as far as it had previously been able to move. Similarly the cam following rollers 38 and 39 will be disposed somewhat forwardly from the position shown in Fig. 1. When the thrust member 15.9 is again moved forwardly with respect to the shaft 35 the cam following rollers 33 and 39 move through a shorter distance and the shaft 35 will be turned through a smaller arc. As a result the torque applied to the workpiece is somewhat less (6 inch pounds instead of 8).

rThe adjustment of screw 55 is the Zero setting for the torsion wrench and when this screw is initially adjusted, no further adjustment thereof is ordinarily necessary. rlhe adjustment of the torque applied will normally be substantially entirely controlled by the adjustment of the position of sleeve 22.

Thejruggedness of the tool is exemplified 'by the fact that the tool in testing, wasr operated 365,000 times, accurately, before becoming inoperative. It will be seen tha-t the torsion rod is easily replaceable.

The form of the invention shown in Fig. 4 is very similar to that shown in Figs. 1 3, with the exception that this form of the ltool is adapted for power operation. The tool shown in Fig. 4 has a shaft 70 with helical guideways or grooves 71 therein. The shaft '70 is hollow and a torsion rod 72 extends therethrough, the rear end of the torsion rod being afxed to the rear end of the shaft 7@ by a pin 73, and the forward end of the torsion rod 72 being affixed by means of pin '74 to a coupling element 75 which has a suitable socket 76 formed therein for releasable attachment with a workpiece 'or an adapter. A rigid cylinder or tubular member 77, in concentric and encompassing relation with shaft 7?, carries the shaft 70 in bearings 73 and 79 in concentric relation with the torsion rod 72. Itwill be noted that the rear end portion 80 of shaft 70 is diminished in diameter as compared to the forward portion thereof.

A hollow thrust mem'ber or piston 81 is disposed within the cylinder 77 and in concentric and encompassing relation with the shaft 70 and has a sealing ring 82 thereon engaging the inner peripheral wall of the cylinder 77 to provide an air-sealing relation therebetween. The diminished rear end portion 80 of shaft 70 projects through an opening 83 in the end wall 34 of piston 81 in an air-sealing but slidable relation.

Cam followers 85 and 86 are disposed in the helical guideway 71 of shaft 70 and are carried by the thrust member or piston 81 on stud shafts 87 which are fixed to the thrust member 81 in a sweat iit.

A fitting 88 is provided at the rear end of cylinder 77 to introduce air under pressure into the chamber 89 for moving the piston 81 forwardly and for turning the shaft 70.

The cylinder 77 is slotted at 90 to receive a piston guide and indicator 91 and permit longitudinal movement of the indicator in the slot. The indicator 91 is affixed to the forward end `of the thrust member or piston 81. The cylinder 77 has a scale 92 imprinted thereon adjacent the slot 90 and the scale may be calibrated in inch pounds of torque.

The cylinder 77 may have a stud 93 aixed on 4the rear end thereof and adapted for coupling with a source of rotary power such as a motor (not shown), whereby to facilitate rapid rotation of the entire tool for turning up a bolt being fastened, after which torque pressure may be applied into the chamber 89 to cause forward movement of the piston 81 and rotation `of the shaft '70, which rotates the rear end of the torsion rod 72 and causes application of torque at the forward end thereof and at the coupling element 75 :which applies the torque to the workpiece may be controlled. In this form of the invention, the torque is applied to the workpiece by manually turning the element 75 to thereby move the piston 8l forwardly so that the indicator 91 stops at a desired scale index such as 7, after which the coupling element 75 is applied to the workpiece and then the air pressure isapplied in the chamber 89 so as to move the piston forwardly causing rotation of the shaft 76 and application of torque to the workpiece.

It will be seen that I have provided a new and improved tOol for readily and easily applying, successively identical predetermined torques to any number `of workpieces by merely moving Ithe thrust member longitudinally along the torsion bar or rod until the movement of the thrust member is stopped. The torsion tool will reset itself so as to be prepared to apply the same identical torque `to the next workpiece.

It will, of course, be understood that various changes may be made in the form, detail, arrangement and proportion of the parts, without departing yfrom the scope of my invention which consists of the matter described herein and set forth in the appended claims.

What I claim is:

1. A thrust type torque wrench, comprising an elongated torsion bar having front and rear ends rotatable with respect to each other within the elastic limit of the bar, coupling apparatus -aflixed to the front end of the bar and adapted for non-rotatable and removable attachment with a workpiece to be turned, a pair of cooperating cam parts, one of said parts being a helical cam, the other of said parts being a cam follower, said cam parts being relatively rotatable and being movable relative to each other along the rotation axis, means connecting one of said cam parts with the rear end of the bar, and means maintaining said cam parts in coopera.- tive camming relation, whereby linear movement of one of the cam parts with respect to the other of the cam parts produces rotation of the rear end of the bar and causes application of torque to the workpiece.

2. A thrust type torque wrench, comprising an elongated torsion bar having front and rear ends rotatable with respect to each other within the elastic limit of the bar, coupling apparatus aflixed to the front end of the bar and adapted for non-rotatable removable attachment with a workpiece to be turned, a thrust element, a pair of cooperating cam parts, one of said parts being a helical cam, the other of said parts being a cam follower, said cam parts being relatively rotatable and being movable relative to each other along the rotation axis, means connecting one of said cam parts with the rear end of the bar, means connecting the other of said cam parts to the thrust element, whereby linear movement of the thrust element produces rotation of the rear end of the bar and causes application of torque to the workpiece.

3. A thrust type torque wrench, comprising an elongated torsion bar having front and rear ends rotatable with respect to each other within the elastic limit of the bar, coupling apparatus aixed to the front end of the bar and adapted for non-rotatable removable attachment with a workpiece to be turned, a thrust element, a pair of cooperating camming parts, one of .said parts being a helical cam, the other of said parts being a cam follower, said cam parts being relatively rotatable and being movable relative to each other along the rotation axis, means connecting one of said cam parts with the rear end of the bar, means connecting the other of said cam parts to the thrust element, and means rigid with the front and rear ends of the bar Aand preventing transverse iiexing of the bar and including a rotary connection permitting relative rotation of the ends of the bar, whereby movement of the thrust element along the rotation axis produces rotation o-f the rear end of the bar and causes application of torque through the front end of the bar to the workpiece without permitting appreciable flexing of the torsion bar.

4. A thrust type torque wrench, comprising an elongated torsion bar having front and rear ends rotatable with respect to each other Within the elastic limit of the bar, coupling apparatus -axed to the front end of the bar and adapted for attachment with a workpiece to be turned, a pair of cooperating cam parts, one of said parts being a helical cam, the other of said parts being a cam follower, said cam parts being relatively rotatable and being movable relative to each other along the rotation axis, means connecting the helical cam to the rear end of `the bar, a generally tubular thrust element encompassing the helical cam and slidable therealong, and means connecting the cam follower to the thrust element, whereby the thrust element maintains the follower in cooperative camming relation with respect to the helical cam and whereby movement `of the thrust element along the helical cam produces rotation of the rear end of the bar and causes application of torque to the workpiece.

5. A thrust type torque wrench, comprising an elongated torsion bar having front and rear ends rotatable with respect to each other within the elastic limit of the bar, coupling apparatus aixed to the front end of the bar and adapted for non-rotatable removable attachment with a workpiece to be turned, an elongated rotary member concentric with the bar and fixed to the rear end of the bar, said rotary member having means defining a helical cam, a cam follower cooperatively engaged with the cam and movable linearly along the rotation axis causing rotation of the rotary member, guide means maintaining the cam and follower in cooperative camming relation and rigid means connecting the rotary member with the front end of the bar whereby to prevent transverse flexing of the bar and said rigid means including a rotary bearing concentric with the rotation axis, whereby to permit rotation of the rotary member with respect to the front end of the bar, whereby linear movement of said camfollower produces rotation of the rear 7 end of the bar and causes application of torque to the workpiece.

' 6. The invention set forth in claim 5, wherein said rigid means includes a rigid member alhxed to the rotary member for rotation therewith, said rigid member ex* tending along the bar to the front end thereof, and said rotary bearing rotatably interconnecting said rigid member and the front end of the bar.

7. The invention 'set forth in claim 5, wherein said guide means includes a hollow piston connected to the cam follower and encompassing the helical cam, said piston projecting rearwardly from the helical cam, and said rigid means including a cylinder enclosing the piston, said cylinder having a portion projecting forwardly adjacent the forward end of the torsion bar, and said rotary bearing being disposed between said forward portion and the forward end of the bar to permit rotation of the forward end of the bar with respect to the cylinder, and means for introducing fluid pressure into the cylinder, whereby to move the piston and cam follower along the helical cam for rotating the rear end of the torsion bar and applying torque to the workpiece.

8. A thrust type torque wrench, comprising an elongated torsion bar having front and rear ends rotatable with respect to each other within the elastic limit of the bar, coupling apparatus affixed to the front end of the bar and adapted for attachment with a workpiece to be turned, a pair of cooperating cam parts, one of said parts being a helical cam, the other of said parts being a cam follower, said cam parts being relatively rotatable and being movable relative to each other along the rotation axis, means connecting one of said cam parts with the rear end of the bar, means maintaining said cam parts in cooperative camming relation, stop means limiting the relative movement of the cam parts in one direction along the rotation axis, and additional stop means limiting relative movement of the cam parts in the other direction along the rotation axis, whereby to limit the maximum torque applicable through the front end of the bar to the workpiece.

9. The invention set forth in claim 8 wherein one of the stop means is adjustable to vary the magnitude of movement of the cam parts relative to each other and thereby vary the maximum torque applicable to the workpiece.

l0. A thrust type torque wrench, comprising an elongated torsion bar having front and rear ends rotatable with respect to each other within the elastic limit of the bar, coupling apparatus ar'lixed to the front end of the bar and adapted for attachment with a workpiece to be turned, a rotary member concentric with the torsion bar and having a forward tubular potion encompassing the bar and rotatably connected with said coupling apparatus, said rotary member also having a rear portion with a helical cam formed therein, said rear portion being affixed to the read end of the torsion bar, a cam follower engaging the helical cam, a tubular thrust member encompassing the helical cam and being affixed to said cam follower for moving the same, said thrust member having a forwardly extending portion including a stop closely adjacent the forward tubular portion of the rotary member, said rotary member also having a stop spaced rearwardly along said tubular forward portion from said first mentioned stop for engagement therewith when said thrust element is moved rearwardly along the helical cam, whereby to denne the starting position of said cam follower with respect to the helical cam and thereby limit the arc through which the rear end of the torsion bar may be turned and also limit the maximum torque applied to the workpiece.

1l. The invention set forth in claim l0 wherein one of said stops is adjustable along the tubular forward portion of the rotary member, and stop means limiting the forward movement of the thrust member and the cam follower along the helical cam, whereby to accurately con trol and vary the magnitude of torque applicable to theworkpiece.

lZ. A thrust type torque wrench, comprising an elon-` gated torsion bar having front and rear ends: rotatable, with respect to each other within the elastic limit of the means rotatably connecting the forward portion of the` rotary member with the coupling apparatus, means securing the rear end of the enlarged portion with the rear end of the torsion bar, said enlarged rear portion defining a helical cam, a tubular thrust member in concen tric and encompassing relation with the helical cam and being slidable longitudinally therealong, a cam follower on the thrust member and engaging the helical cam in cooperative camming relation, to produce rotation of the rotary member as the thrust member is moved therealong, a sleeve in concentric and encompassing relation with the diminished forward portion of the rotary lmember and being slidable longitudinally therealong, said sleeve and the forward end of the tubular thrust member being telescopically related, releasable locking means between the thrust member and the sleeve for adjustably fixing the relative positions thereof, the rear end of the sleeve and the forward end of the enlarged portion of the rotary member being engageable in abutting relation to restrict rearward sliding of the thrust member and sleeve along the rotary member and define the starting position of the rotary member, to thereby limit the arc of rotation through which the rotary member and the rear end of the torsion bar may be turned, and abutment means limiting the forward movement of the thrusty member along the rotary member, whereby the sleeve may be adjusted with respect to the thrust member to vary the maximum torque applicable to the workpiece.

13. A thrust type torque wrench comprising an elongated torsion bar having front and rear ends rotatable with respect to each other within the elastic limit of the bar, coupling apparatus aixed to the front end of the bar and adapted for attachment with a workpiece to be turned, a tubular rotary member in concentric encompassing relation with the torsion bar and having forward and rear portions, means rotatably connecting the forward portion of the rotary member with the coupling apparatus, means securing the rear portion of the rotary member to the rear portion of the torsion bar, said rear portion of the rotary member having a helical cam in the periphery thereof, a tubular thrust member in concentric and encompassing relation with the rotary member and slidable therealong, a cam follower on the thrust member and engaging the helical cam in cooperative camming relation, to produce rotation of the rotary member as the thrust member ismoved therealong, cooperating stop means on the thrust member and rotary member, whereby to limit rearward sliding movement of the thrust member along the rotary member, an abutment on the rear end of the thrust member and a longitudinally adjustable stop on the rear end of the rotary member and positioned for engagement with said abutment, whereby to limit the forward sliding movement of the thrust member on the rotary member, whereby adjustment of said stop varies the torque applicable to the coupling apparatus.

14. A thrust type torque wrench, comprising an elon-v gated torsion bar having front and rear ends rotatable with respect to each other within the elastic limit of the bar, coupling apparatus aflixed to the front end of the bar and adapted for non-rotatable removable attachment with a workpiece to be turned, a helical cam concentric with the bar rotation axis and aiixed to the rear end of the bar, a cam follower in cooperative camming relation with the helical cam and movable linearly along the rotation axis to produce rotation of the cam, means maintaining the cam follower in cooperative camming re lation with the cam and including a thrust element connected with said follower for moving the same linearly along the rotation axis and producing rotation of the rear end of the bar and application of torque to the workpiece.

References Cited in the file of this patent UNITED STATES PATENTS Wolfram June 25, 1940 Werner Nov. 5, 1946 Jackson .Tune 24, 1947 Greer June 7, 1949 FOREIGN PATENTS France Aug. 22, 1951 

